Simple inverter circuit

[EWBrown]

This may be a good basis for a "mobile" tube amp power supply, best of all, it uses inexpensive and easily available parts.

Found it during a "random" web search.



"OPT" looks to be a 12VCT filament transformer. Run the "AC" frequency higher than 60 Hz, try 200 to 400 Hz, perhaps.

Useit with one of the potted Triad inverter toroids, like TY-78, TY-81, TY-84, etc, run at 2KHz, and the potting should muffle the core's "whine"

YMMV, etc...

/ed B

[Geek]

I have a couple genuine inverter transformers. Might be worth a try

[TerrySmith]

This gives me some ideas for a simple tube amp for the car.

How big should the transformer be if you were to build a RH-84 type of amp? I don't really need a lot of power, just something that sounds decent and plays at normal listening levels.

As a sidenote I recently picked up a Boss Audio "mechless" car radio, it's AM-FM, no CD player, and has a USB and SD card slots for playing MP3 and WMA files. It only cost $35.00 at Amazon. The downside is it's rated at 200w, but it sounds like four transistor radios at full blast! I would like to know where they get that rating from. However, it does have RCA outs and hooked to a ST-70 on the bench it does sound quite good!

[EWBrown]

For an RH-84, I'd design it for 325VDC, at least 100 mA, wouldn't hurt to have more available current.
A 10VAC CT filament tranny (at least 5A rating, 10 would not be excessive) from Hammond should be a good choice here.
Since the plan is to run it at a higher "AC" frequency, the normal turns-per-volt formula for 60 Hz can be stretched by (roughly)
a factor of F(hz)/60, though the core size doesn't become any smaller.

I'd consider connecting a .001 uF 1KV ceramic disc cap across the HV AC output, in order to tame the possible "ringing"
and reduce the possibility of getting a whine or buzz worming its way through the rectifiers and DC filtering.

With this circuit, the AC wave form will be more square wave, than sinusoidal, peak-to-peak voltage
versus RMS voltage calculations aren't necessary. WYSIWYG An open-frame tranny will probably howl or buzz with higher frequency
operation, I'd suggest to build the PSU on a separate chassis.

I have a couple of "real" inverter transformers, but they were designed for using germanium power transistors,
though they should work with this circuit, operating about 2 KHz. One is a potted Triad TY-78, the other one
is open frame, and can handle considerable power, about 150VA, at least. IIRC, this was good for 600VDC and 300VDC.
I long ago lost the data sheet for it, so some experimentation will be needed.

The HV inverter power supply that I built with the other identical transformer, I sold at a hamfest back in the 1980s...

The car radio was probably designed for use with 2 ohm speakers, and the "200 watts" must use the same kind of Roswell UFO
alien technology as my "400 watt" computer speakers, which are powered by a 12VDC, 1A brick

/edB